Spectrophotometric Determination of Lysine in Drugs with 1,2-Naphthoquinone-4-Sulfonate as Colour Reagent

In a borate buffer of pH 9.6,based on the nucleophilic substitution reaction between lysine and sodium 1,2-naphtoquinone-4-sulfonate,a salmon pink colored compound with mole ratio of 1 to 2 was formed.The absorption maximum of this colored compound was found at the wavelength of 474 nm,and the absorption absorptivity (ε474) found was 5.1×103L·mol-1·cm-1.Linear relationship between values of absorbance and concentration of lysine was kept in the range of 0.2-55 mg·L-1,with detection limit (3s/k) of 0.16 mg·L-1.The proposed method was applied to the determination of lysine in drug samples,and test for recovery was made by adding standard lysine solution to these samples,giving values of recovery ranged from 99.0%-100.3%,and values of RSD′s (n=5) less than 0.55%.